,a ,,plan                               
,,=                    ,,secur+         
,,obs]vations                           
,,( ,,!                       ,,v>iable 
,,/>s4                              ,,by
                    ,,edw>d ,c4         
,,pick]+1         ,,director ,,( ,,!    
,,h>v>d ,,college ,,obs]vatory4         
,,cambridge3                    ,,john  
,,wilson ,,& ,,son4                     
,univ]sity ,press                       
#ahhb4                      ,a ,,plan   
,,= ,,secur+ ,,obs]vations              
,,( ,,! ,,v>iable ,,/>s4                
,,= sev]al reasons ! inve/igations "h   
propos$ are especially suit$ to obs]v]s 
"u v v>i\s conditions4 ,! "w is capable 
( indef9ite sub-division4 ,small z well 
z l>ge telescopes may be employ$ & _m   
obs]vations are ne$$ :i* c be/ be made )
 an op]a-glass or field-glass1 or ev5 ) 
! nak$ eye4 ,no atta*m5t is ne$$ to an  
ord9>y telescope1 s t no additional     
exp5se on ?is acc\nt is requir$4 ,useful
 obs]vations may be made by an unskill$ 

obs]v] provid$ t he is capable (        
id5tify+ a /> ) c]ta9ty4 ,! "w is       
quantitative1 & ! obs]v] has1 !re=e1 a  
cont9ual te/ ( ! increas$ accuracy he   
has acquir$ by practice4 ,z a portion ( 
! inve/igation w probably lead to !     
discov]y ( int]e/+ objects1 !           
obs]vations w possess an int]e/ (t5     
want+ 9 quantitative rese>*4 ,! aid ( ! 
pr(essional a/ronom] is e>ne/ly reque/$ 
= ?is s*eme4 ,sugge/ions by :i* x may be
 modifi$ & improv$ w be gratefully      
receiv$4 ,! pr(essional a/ronom]1 9     
consequ5ce ( 8 great] skill1 in/rum5tal 
appliances1 & comm& ( 8 own "t1 c\ld    
fill gaps 9 ! "w1 & ?us greatly increase
 its value z a :ole4 ,su* obs]vations   
c\ld (t5 be made 9 ! int]vals ( o!r "w  
or at times unsuitable = ! obs]vations  
to :i* he 0 especially devot+ himself4  
,x %\ld be add$ t especial c>e w be tak5
 n to int]f]e ) obs]vations ( v>iable   
/>s n[ 9 progress4 ,obs]v]s ( ^! objects
 are p>ticul>ly reque/$ to notify !     
writ] :at "w !y propose to c>ry out1 s t

 a ne$less repetition ( x may be avoid$4
  ,x is on ! amateur & /ud5t ( a/ronomy 
t we mu/ dep5d l>gely = ! success ( !   
plan "h propos$4 ,_m su* p]sons sp5d    
ev5+ aft] ev5+ at _! telescopes )\t     
obta9+ results ( any p]man5t value4     
,ei!r no publication is made & ! results
 are !re=e valueless1 or "t is sp5t on  
objects t c be mu* m usefully exam9$ ) a
 l>g] in/rum5t4 ,mo/ commonly ! obs]v]  
has no special plan & sp5ds _m h\rs )\t 
result1 :ile ! same "t might h be5      
employ$ ) equal pleasure to himself &   
results ( great value collect$4 ,^? :o h
 n tri$ x d n realize ! gr[+ int]e/ 9 a 
sy/ematic rese>* & ! satisfaction 9     
feel+ t by "o's own labors ! sum ( human
 k has be5 increas$4  ,mu* valuable     
assi/ance might be r5d]$ by a class ^:  
aid 9 su* "w has usually be5 ov]look$4  
,_m ladies are int]e/$ 9 a/ronomy & own 
telescopes1 b ) two or ?ree notewor?y   
exceptions _! contributions to ! sci5ce 
h be5 almo/ no?+4 ,_m ( !m h ! "t &     
incl9ation = su* "w1 & especially among 

! graduates ( wom5's colleges are _m :o 
h _h abundant tra9+ to make excell5t    
obs]v]s4 ,z ! "w may be done at home1   
ev5 f an op5 w9d[1 provid$ ! room has ! 
temp]ature ( ! out] air1 !re seems to be
 no reason :y !y %\ld n ?us make an     
advantage\s use ( _! skill4 ,x is       
believ$ t x is only necess>y to po9t !  
way to secure mo/ valuable assi/ance4 ,!
 criticism is (t5 made by ! oppon5ts ( !
 high] education ( wom5 t1 :ile !y are  
capable ( foll[+ o!rs z f> z m5 c1 !y   
orig9ate almo/ no?+1 s t human k is n   
advanc$ by _! "w4 ,?is reproa* w\ld be  
well answ]$ c\ld we po9t to a long s]ies
 ( su* obs]vations z are detail$ bel[1  
made by wom5 obs]v]s4  ,v>iable />s may 
be def9$ z ^? :i* exhibit a v>y+ degree 
( brightness at diff]5t times4 ,! foll[+
 classification ( !m is believ$ to be a 
natural "o4 7,proc4 ,am]4 ,acad4 xvi1   
#a1 #beg47  ,i4 ,tempor>y />s1 or ^? :i*
 %9e out sudd5ly1 sometimes ) great     
brilliancy1 & gradually fade away4      
,examples1 ,ty*o ,brahe's /> ( #aegb1   

new /> 9 ,corona1 #ahff4  ,,ii4 ,long   
p]iod v>iables1 or ^? und]go+ great     
v>iations ( light1 ! *anges recurr+ 9   
p]iods ( sev]al mon?s4 ,examples omicron
 ,ceti & *i ,ceti4  ,,iii4 ,/>s und]go+ 
slight *anges accord+ to laws z yet     
unkn[n4 ,examples1 alpha ,orionis &     
alpha ,cassiopeiae4  ,,iv4 ,%ort p]iod  
v>iables1 or />s ^: light is cont9ually 
v>y+1 b ! *anges are repeat$ ) great    
regul>ity 9 a p]iod n exce$+ a few days4
 ,examples1 beta ,lyrae & delta ,cephei4
  ,v4 ,algol />s1 or />s :i* = ! great] 
portion ( ! "t und]go no *ange 9 light1 
b e few days suff] a rem>kable dim9ution
 9 light = a few h\rs4 ,?is ph5om5on    
recurs ) su* regul>ity t ! int]val      
betwe5 successive m9ima may be det]m9$ 9
 "s cases )9 a fraction ( a second4     
,examples beta ,p]sei 7,algol7 & ,s     
,cancri4  ,/>s belong+ to ! fir/ ( ^!   
classes are se5 s r>ely t ! app>5t      
discov]y ( "o is to be receiv$ ) ! utmo/
 caution4 ,on ! o!r h&1 ! importance (  
e>ly obs]vations ( su* an object is s   

great t no pa9s %\ld be sp>$ to secure  
an e>ly ann\ncem5t if "o is really f\nd4
 ,on ! be/ /> *>ts _m />s are omitt$ ( !
 brightness ( ! fa9te/ objects giv54 ,b 
any /> mu* bright] ?an ^! %\ld be       
measur$ by ! me?od giv5 bel[1 & a wat*  
kept to see if any *ange takes place4   
,if x proves to be a tempor>y /> an     
imm$iate ann\ncem5t %\ld be made4 ,if a 
telegram is s5t to ?is ,obs]vatory !    
object w be at once exam9$1 &1 if       
v]ifi$1 notification w be made 9 ?is    
c\ntry & 9 ,europe ) ! "n ( ! discov]]  
or s5d] ( ! telegram4 ,a simil>         
notification may be s5t ( any suspect$  
objects1 :i* w be exam9$ 9 ! same way1 &
 ann\nc$ at once if !y prove to be (    
int]e/4 ,x is ess5tial t ! position ( ! 
object %\ld be giv5 ) all ! precision   
practicable1 & t a lett] %\ld be s5t by 
! next mail giv+ ! obs]vations 9 detail4
 ,?is (t5 proves ( ! greate/ value 9    
case ! object is n readily f\nd4 ,x also
 s]ves to e/abli% ! claims ( ! fir/     
discov]]4  ,ne>ly ?ree qu>t]s ( ! kn[n  

v>iables belong to ! second class4 ,mo/ 
( !m und]go v l>ge *anges ( light1 & may
 !re=e be obs]v$ ) comp>ative ease4 ,our
 k ( _! v>iations is h[ev] v defective4 
,hi!rto ! att5tion ( obs]v]s has be5    
direct$ pr9cipally to det]m9+ ! times at
 :i* !y atta9 _! maximum light1 :ile _! 
light at int]m$iate times has be5       
neglect$4 ,x is n[ propos$ to secure    
obs]vations ( ^! objects once or twice 9
 e mon?1 s t _! light curves or         
v>iations ?r\gh\t _! entire p]iods may  
be det]m9$4 ,aga91 _m obs]v]s are       
accu/om$ to /ate _! brightness 9        
magnitudes )\t giv+ any clue to ! scale 
:i* !y employ4 ,9 mo/ cases su*         
obs]vations h little value ow+ to !     
unc]ta9ty ( ! scale ( ! fa9t]           
magnitudes4  ,accord+ to ,dr4 ,g\ld & "s
 o!r obs]v]s mo/ ( ! visible />s und]go 
slight *anges ( light & %\ld !re=e be   
assign$ to ! ?ird class ( v>iables4 ,x  
is probable t our ,sun also belongs to  
?is class1 z x is n likely t its light  
is ! same dur+ ! maximum & m9imum ( !   

sun spot p]iod4 ,at pres5t we are unable
 to tell 9 :i* case ! light w\ld be     
greate/4 ,x by no means foll[s t :5 !   
spots are mo/ abundant ! ,sun's total   
light is lea/1 = ! rema9+ portions ( !  
,sun may !n h an increas$ brightness m  
?an comp5sat+ = _! dim9i%$ area4 ,z long
 z ! suspect$ v>iations 9 light ( ! />s 
are small1 n exce$+ half a magnitude =  
in/ance1 !y seem 9 ! pres5t /ate (      
sci5ce to h comp>atively little int]e/4 
,!y are s liable to be affect$1 or ev5  
caus$1 by errors ( obs]vation1 t !      
obs]vation ( su* objects does n seem n[ 
to be advisable4 ,d\btless _m su*       
s-call$ v>iables are really due to      
errors caus$ by moonlight1 ! proximity (
 bright] />s1 v>y+ position ( ! images  
on ! ret9a ( ! obs]v]1 & o!r simil>     
causes4 ,!y w n !re=e be consid]$ fur!r 
9 ?is pap]4  ,! />s ( ! f\r? class z    
comp>$ ) ! second are relatively few 9  
numb]1 & ! *anges 9 light small4 ,:ile  
_m ( !m ne$ obs]vation1 especially to   
det]m9e _! light curves m precisely1 x  

is advis$ t ?is "w be left to ^? :o h   
acquir$ a high degree ( skill 9 ^!      
obs]vations4 ,t ! "w may be ( value x is
 ess5tial t ! errors %\ld be extremely  
small4 ,z1 h[ev]1 ne>ly all are visible 
9 an op]a-glass1 a skilful obs]v]       
unprovid$ ) a telescope may secure      
valuable results by _! obs]vation4 ,?is 
rem>k applies ) especial =ce to _m ( ^? 
discov]$ 9 ! s\!rn heav5s by ,dr4 ,g\ld4
  ,! ph5om5a ( ! ,algol />s are 9 _m    
respects ! mo/ /rik+ ( any4 ,! rapidity 
( ! *anges1 _! surpris+ regul>ity1 & !  
comp>ative r>ity ( ^! objects1 comb9e to
 r5d] ! discov]y ( ea* new "o a matt] ( 
unusual int]e/4 ,z 9 ! case ( />s ( !   
f\r? class1 h[ev]1 ! /udy ( _! light    
curves %\ld be left to ^? :o h acquir$  
especial skill 9 ?is "w4 ,?is is        
p>ticul>ly desirable1 :51 z 9 ?is case1 
! unaid$ eye ent]s into competition )   
photometric app>atus1 by :i*1 z "s ?9k1 
x %\ld prop]ly be altoge!r replac$4  ,an
 elaborate bibliographical "w on !      
v>iable />s has be5 und]tak5 at ?is     

,obs]vatory by ,mr4 ,*&l]4 ,x w include 
! collection ( all available publi%$    
obs]vations ( kn[n or suspect$ v>iables4
 ,a catalogue ( suspect$ v>iables has   
?us be5 prep>$1 d\btless conta9+ _m />s 
:i* are really important v>iables4 ,b x 
is also likely t _m objects h be5       
introduc$ 9 ! li/ by errors 9 ! orig9al 
obs]vations4 ,su* />s (t5 appe> 9 "o    
catalogue aft] ano!r ( suspect$         
v>iables1 & x is difficult to prev5t !  
cont9u$ circulation ( su* an error4 ,(  
c\rse if an exp]i5c$ obs]v] at any "t   
e/imates a /> z above or bel[ its normal
 brightness1 x is impossible to prove t 
! obs]vation 0 n correct1 & ! /> really 
v>iable4 ,no am\nt ( subsequ5t obs]v+   
c\ld prove t x _h n !n1 & !n only1 an   
abnormal brightness4 ,we c1 h[ev]1 prove
 t 9 all probability x does n belong to 
"o or m ( ! above classes1 & ?us make x 
m & m probable t ! obs]vation is due to 
an error4 ,if ! /> v>ies 9 light by "o  
magnitude1 :at w be ! *ances t we %all  
get a s]ies ( obs]vations hav+ a range (

 v>iation ( "o fif? ( a magnitude8      
,evid5tly on ! av]age1 !re w be only "o 
*ance out ( five t any obs]vation %all  
fall 9 ! same fif? ( a magnitude z      
ano!r4 ,! *ances = ?ree su* obs]vations 
w be only #a_/be & = f\r #a_/abe1 etc4  
,^! ratios express$ decimally are 4#b1  
4#jd1 4#jjh1 #jjaf1 4#jjjc1 etc4 ,s9ce !
 sep>ate det]m9ations ( ! light ( a     
con/ant /> by ! me?od giv5 bel[ %\ld n  
diff] m ?an two or ?ree t5?s ( a        
magnitude1 x is obvi\s t if ! v>iations 
( ! /> are l>ge1 a few obs]vations w\ld 
g5]ally e/abli% ?is fact4 ,if ! />      
belongs to class f\r1 obs]vations on    
half a doz5 ev5+s w\ld h>dly fail to %[ 
! v>iation4 ,conv]sely1 if no su*       
v>iation is detect$ we may be almo/     
c]ta9 t ! /> is n a v>iable ( t class1  
or at lea/ t ! v>iation1 if any1 is n   
l>ge4 ,if ! /> belongs to class two1 x w
 *ange s sl[ly :5 ne> its maximum or    
m9imum t a v>iation might n be not$ if !
 obs]vations are ne> toge!r4 ,an int]val
 ( sev]al mon?s %\ld !re=e be all[$ to  

take place1 or p]haps x w\ld be bett] to
 wait until ! /> is aga9 visible !      
foll[+ ye>4 ,! total v>iation 9 light is
 usually s great 9 ^! />s t ! *ange w   
(t5 be visible at ! fir/ glance4  ,to   
prove t a /> does n belong to ! fif?    
class is a matt] ( mu* great]           
difficulty4 ,9 fact x is almo/          
impossible to prove t x may n be an     
,algol /> ) a long p]iod betwe5 ! m9ima4
 ,s9ce ^! />s may h _! full brightness =
 n9e t5?s ( ! "t1 x is obvi\s t !y may  
be exam9$ aga9 & aga9 )\t happ5+ to be  
se5 at ! "t ( a m9imum4  ,on ! o!r h&1  
dur+ a consid]able portion ( ! "t :5 x  
is v>y+1 ! light w be s mu* less ?an    
usual t a c>eful measurem5t is n ne$$ to
 detect ! *ange4 ,moreov]1 x w be       
useless to look = an increase ( light1 &
 ! obs]vation may be s plann$ z to      
detect a dim9ution only4  ,if we assume 
t only dur+ "o t5? ( ! "t ! *ange 9     
light w be suffici5t to be p]ceptible1 !
 *ance on any giv5 ev5+ w be #i out (   
#aj or #i_/aj t ! /> w h its full       

brightness4 ,= two ev5+s ! *ance w be   
7#i_/aj7b = ?ree 7#i_/aj7c1 etc4 ,^!    
quantities express$ decimally are 4#i1  
4#ha1 4#gc1 4#ff1 4#ei1 4#ec1 4#dh1 etc4
 ,ev5 aft] sev5 nights' obs]vations1 on 
:i* no *ange is not$1 x w only be ab\t  
an ev5 *ance t ! /> may n /ill be ( !   
,algol type4 ,a diff]5t me?od ( obs]v+  
is !re=e recomm5d$ :5 ! /> is suppos$ to
 belong to ?is class4 ,select =         
comp>ison a /> slightly fa9t]1 s t a    
mom5t's glance w satisfy ! obs]v] t !   
suspect$ v>iable is ! bright]4 ,x is    
only necess>y to repeat ?is obs]vation  
night aft] night4 ,if ! /> is bright    
en\gh to be visible ) a field glass1 a  
few seconds w be suffici5t = ?is        
obs]vation aft] ! obs]v] has become     
famili> ) ! vic9ity4 ,! fact t ! light  
is normal1 & ! "t to ! ne>e/ m9ute1 %\ld
 be record$ aft] ea* obs]vation4 ,:5    
conv5i5t1 x is well to repeat !         
inspection two or m times dur+ ! night1 
z 9 det]m9+ ! p]iod all ! obs]vations w 
h a value1 provid$ t !y are sep>at$ by  

int]vals ( m ?an two or ?ree h\rs4 ,if !
 /> is ev] f\nd bel[ its normal         
brightness1 comp>isons %\ld be made ) ! 
adjac5t />s1 & cont9u$ z long z         
possible1 or until x has rega9$ its     
usual brightness4 ,! mo/ complete pro( t
 a /> 0 n ( ! ,algol type w\ld be =     
obs]v]s 9 ! pol> regions to exam9e x at 
int]vals ( a few h\rs = sev]al days1 or 
= obs]v]s 9 diff]5t longitudes to make !
 same obs]vations4 ,if x c\ld ?us be    
wat*$ = a week or =tnight by en\gh      
obs]v]s to avoid int]f]5ce by cl\ds1 x  
w\ld be ne>ly c]ta9 t x is n an ,algol  
/> unless its p]iod is great] ?an t (   
any su* object z yet discov]$4  ,!      
problems to be und]tak5 may be def9$ z  
foll[s3--  #a4 ,to obs]ve all ! long    
p]iod v>iables once or twice e mon?     
?r\gh\t _! v>iations accord+ to su* a   
sy/em t all ! obs]vations may be r$uc$  
to ! same absolute scale ( magnitudes4  
#b4 ,to obs]ve ! />s ^: v>iability is   
suspect$ & prove ei!r t !y are really   
v>iable1 or t 9 all probability !y d n  

belong to ! fir/1 second1 or f\r? class4
 ,if any are ?\ght to belong to ! fif?  
class1 to wat* !m until su* a v>iation  
is prov$1 or is %[n to be improbable4   
,all ( ?is "w w dep5d on ! possibility (
 readily det]m9+ ! brightness ( a />    
accord+ to su* a me?od t all !          
obs]vations c ultimately be r$uc$ to !  
same sy/em4 ,h]s*el & ,argel&] h        
indep5d5tly inv5t$ :at appe>s to be !   
true me?od to be foll[$4 ,if a /> is se5
 to be v ne>ly equal to sev]al o!rs1 f  
_! light we c at any "t def9e its       
brightness4 ,x is ess5tial t at lea/ "o 
( ! />s select$ %\ld be a little        
bright]1 ano!r a little fa9t]1 ?an ! /> 
to be obs]v$4 ,! range )9 :i* its light 
is kn[n is ?us also def9$4 ,su*         
obs]vations w f> exce$ 9 value any      
direct e/imate ( magnitude4 ,:5 />s are 
to be comp>$ _m times1 x is conv5i5t to 
designate !m by lett]s = brevity4 ,let v
 repres5t a /> :i* is suspect$ to be    
v>iable1 & a an adjac5t /> ( ne>ly equal
 brightness4 ,ow+ to fluctuations 9 !   

atmosph]e1 ea* /> w appe> to be         
con/antly v>y+ 9 brightness4 ,if ! />s  
appe> equal aft] a c>eful exam9ation1 or
 if "o appe>s bright] z (t5 z x appe>s  
fa9t] ?an ! o!r1 we may d5ote ?is       
equality by av or va1 ^! t]ms hav+      
precisely ! same mean+4 ,if "o ( ! />s  
is suspect$ to be bright]1 t is1 if x   
appe>s sometimes bright] & sometimes    
fa9t]1 b m frequ5tly bright]1 ! int]val 
may be designat$ z "o grade4 ,!         
obs]vation may be writt5 a #a v or v #a 
a1 ! brighte/ /> be+ nam$ fir/4 ,if "o  
/> is c]ta9ly bright] ?an ! o!r1 !      
diff]5ce1 h[ev]1 be+ v small1 s t !y    
sometimes appe> equal1 ! diff]5ce w be  
two grades1 & may be writt5 a #b v or v 
#b a4 ,great] int]vals may be e/imat$ z 
?ree or f\r grades1 b su* obs]vations h 
mu* less value4 ,x is f\nd 9 practice t 
a grade ?us e/imat$ w slightly exce$ a  
t5? ( a magnitude4 ,a useful ex]cise =  
an obs]v] is to select two />s ( kn[n   
magnitude & sev]al o!rs ( int]m$iate    
brightness4 ,arrange !m 9 a s]ies 9 !   

ord] ( brightness1 & e/imate ! int]vals 
9 grades4 ,! diff]5ce 9 magnitude ( !   
fir/ />s divid$ by ! total numb] (      
grades gives ! value ( "o grade4 ,by us+
 diff]5t int]m$iate />s1 ! same /&>d />s
 may be employ$ repeat$ly4 ,! foll[+    
well-kn[n pol> />s w be conv5i5t1 s9ce  
!y are always visible3-- a alpha ,ursae 
,m9oris1 #b4b magn42 gamma ,ursae       
,m9oris1 #c4j magn42 delta ,ursae       
,m9oris1 #d4d magn42 #ea ,cephi1 #e4d   
magn42 lambda ,ursae ,m9oris1 #f4e magn4
 ,! above me?od is ess5tially t (       
,argel&]4 ,sir ,william ,h]s*el _h      
already employ$ a me?od :i* diff]$ ma9ly
 9 8 notation1 a 4 1 & -- be+ equival5t 
to "o1 two1 or ?ree grades4  ,9 all "w (
 ?is k9d ! obs]v] mu/ look directly at !
 /> he is obs]v+ at ! mom5t1 & nev] try 
to comp>e two />s by a simultane\s      
inspection ( bo?4 ,aft] exam9+ "o />    
until he has a di/9ct impression ( its  
av]age brightness1 fre$ f ! mom5t>y     
*anges due to atmosph]ic di/urbance1 he 
%\ld obs]ve ! o!r 9 ! same mann]4       

,alt]nate obs]vations ( ! two />s1 ea*  
obs]vation la/+ = a few seconds1 w give 
a tru] impression ?an c be d]iv$ f a    
simultane\s obs]vation 9 :i* ! two      
images mu/ be diff]5tly plac$ on !      
ret9a4  ,! pr9cipal objection to ?is    
me?od is ! difficulty ( det]m9+ ! value 
( a grade1 z x is liable to v>y ) !     
obs]v]1 ! "t1 ! condition ( ! air1 & !  
brightness ( ! />s4 ,^! difficulties are
 avoid$ by ! foll[+ me?od4 ,select two  
/>s = comp>ison2 "o1 a1 slightly bright]
 ?an ! /> to be measur$1 v1 ! o!r1 b1   
slightly fa9t]4 ,! int]val betwe5 a & b 
%\ld nev] exce$ "o magnitude4 ,e/imate !
 brightness ( v 9 t5?s ( ! int]val f a  
to b4 ,?us1 if v is midway betwe5 a & b 
! int]val w be five t5?s1 & we may write
 a #e b4 ,if v is ne>ly z bright z a1 we
 may h a #a b or a #b b2 if v is n mu*  
bright] ?an b1 we may h a #h b or a #i  
b4 ,an advantage ( ?is me?od is t l>g]  
int]vals 9 brightness may be us$ betwe5 
! comp>ison />s1 & accord+ly less di/ant
 />s employ$4 ,an increase 9 di/ance ( !

 />s always r5d]s ! comp>ison m         
difficult4 ,we c also obta9 _m indep5d5t
 comp>isons by us+ sev]al comp>ison />s4
 ,if we h m />s bright] & n fa9t]1 we   
%all only h m  n indep5d5t measures by !
 me?od ( grades1 :ile we may h m n      
comp>isons by e/imat+ t5?s1 s9ce        
e/imates may be made 9 t]ms ( ! int]vals
 betwe5 ea* bright] & ea* fa9t] />4 ,on 
! o!r h&1 especially :5 obs]v+ />s n v  
ne> toge!r1 x is a decid$ advantage to h
 to comp>e two />s r ?an ?ree4 ,ea*     
me?od has its advantages1 & t to be us$ 
%\ld d\btless dep5d on ! temp]am5t ( !  
obs]v]4  ,sev]al precautions are ne$$ to
 secure ! be/ results4 ,no obs]vations  
%\ld be made ne> ! horizon2 &1 :5 !     
objects exam9$ are at any consid]able   
z5i? di/ance1 />s diff]+ sev]al degrees 
9 altitude %\ld be avoid$4 ,if ! />s are
 bright & !re is no *oice1 a correction 
may be made = ! error due to ! v>y+     
absorption at ^! diff]5t altitudes if ! 
"t ( obs]vation has be5 not$4 ,:5 us+ a 
telescope or op]a-glass1 ! />s %\ld be  

br\ght 9 turn to ! c5tre ( ! field1 z :5
 ne> ! edge !y w n appe> ( _! true      
brightness4 ,?is is f\nd to be bett] ?an
 plac+ !m at equal di/ances f ! c5tre4  
,9 select+ comp>ison />s1 ! proximity ( 
a bright] /> is v objectionable1 caus+ a
 l>ge error1 :i* v>ies ) ! magnify+ p[] 
us$4 ,d\ble />s %\ld be avoid$ if ! p[] 
us$ is suffici5t to %[ ! companion4     
,comp>+ />s ( diff]5t colors is also    
objectionable4  ,any p]sons :o desire to
 take "p 9 ^! obs]vations are reque/$ to
 communicate ) ! writ]1 & s5d answ]s to 
! que/ions giv5 bel[4  #a4 ,:at is !    
location ( y\r po9t ( obs]vation8 ,9 !  
city or 9 ! c\ntry1 on ! gr\nd1 f a ro(1
 or f a w9d[8 ,is any "p ( y\r horizon  
ob/ruct$1 or c y obs]ve 9 all p>ts ( !  
sky8  #b4 ,:at is ! ap]ture1 focal l5g?1
 & "n ( mak] ( y\r telescope8 also !    
l[e/ magnify+ p[] & l>ge/ field ( view y
 c obta9 ) x8 ,h y a field-glass or     
op]a-glass8  #c4 ,c y id5tify bright &  
fa9t />s f _! designations or "r        
asc5sions & decl9ations8 ,h y ,heis'    

,atlas ,coele/is ,novus1 ! ,uranometria 
,arg5t9a1 ! ,dur*mu/]ung1 or o!r maps & 
catalogues ( ! />s8  #d4 ,w\ld y pref]  
to obs]ve ! kn[n or ! suspect$ v>iables1
 or to divide y\r "t betwe5 !m8  ,=     
conv5i5ce 9 mak+ ! r$uctions & = future 
ref]5ce1 x is ess5tial t all !          
obs]vations %\ld be made accord+ to !   
same sy/em4 ,obs]v]s are accord+ly      
reque/$ to adopt ! foll[+ =m4 ,use      
half-%eets ( lett] pap] 7eight in*es by 
t571 writ+ only on "o side & leav+ a    
m>g9 ( half an in* = b9d+4 ,beg9 ) a new
 %eet e ev5+1 & write ! date & location 
7t[n%ip & /ate7 on ! fir/ l9e4 ,ea* %eet
 :5 complet$ %\ld be sign$1 & all %\ld  
be numb]$ consecutively4 ,:5 sev]al     
%eets are us$ on ! same night1 ! date   
%\ld be ent]$ on ea*4 ,! record %\ld be 
made 9 p5cil1 & all subsequ5t rem>ks or 
corrections add$ or int]l9$ ) ink1 tak+ 
especial c>e n to oblit]ate or r5d]     
illegible ! orig9al record4  ,a g5]al   
/atem5t %\ld be made ea* ev5+ ( !       
condition ( ! sky1 z cle>1 hazy1 pass+  

cl\ds1 etc4 ,! "t ( beg9n+ & end+ "w    
%\ld also be not$4 ,"o l9e %\ld be      
assign$ to ea* comp>ison4 ,! h\r & m9ute
 %\ld be writt5 to ! left1 & ! comp>ison
 next to x4 ,! "r-h& half ( ! l9e w be  
left blank = r$uc+ ! obs]vation4  ,c]ta9
 ev5+s or portions ( ev5+s mu/ also be  
devot$ to ! selection ( ! comp>ison />s 
( suspect$ v>iables4 ,if !y are conta9$ 
9 maps :i* are available1 ! lett]s      
assign$ to ea* /> may be m>k$ on ! maps 
& l9es drawn to %[ ) :at suspect$       
v>iable /> !y are associat$4 ,if        
pref]r$1 a sket* may be made ( !        
neighbor+ />s & ! lett]s ent]$ on !m4   
,?is sket* ) a prop] description %\ld be
 ent]$ on ! obs]v+ %eets describ$ above1
 & a copy %\ld be reta9$ = ref]5ce4 ,e  
mon? ! obs]vations w be int]rupt$ by    
moonlight1 & accord+ly1 ?ree or f\r days
 be=e ! full moon1 all ! %eets t h      
accumulat$ %\ld be mail$1 address$      
,h>v>d ,college ,obs]vatory1 ,cambridge1
 ,mass4 ,an ackn[l$gm5t w be s5t at     
once1 s t if ?is is n receiv$ a second  

notification %\ld be s5t4  ,to atta9    
success x is p>ticul>ly important t !   
plan %\ld n be local or national4       
,obs]v]s 9 ! s\!rn hemisph]e are mu*    
ne$$1 & = "s purposes ^? 9 v>i\s        
longitudes4 ,x is hop$ t among ! _m     
amateurs ( ,europe1 & especially (      
,engl&1 may be f\nd "s ready to         
p>ticipate 9 ?is "w4 ,no re/riction     
reg>d+ ! obs]vations or publication is  
int5d$2 b x is hop$ t a l>ge addition to
 our pres5t k ( ! v>iable />s may be    
secur$1 )\t int]f]+ ) :at w\ld o!rwise  
be obta9$4 ,copies ( ?is pamphlet &     
fur!r in=mation w be furni%$ on         
application4 ,any p]sons desir+ to      
p>ticipate are reque/$ to address !     
writ]1 s5d+ answ]s to ! que/ions giv5   
above4 ,! details w diff] ) ea* obs]v]1 
& w be arrang$ by correspond5ce4 ,ap>t f
 ! value ( ! results atta9$1 x is       
believ$ t _m amateurs w f9d x a b5efit  
to accu/om !mselves to "w 9 a sy/ematic 
mann]1 & t !y w ?us receive a tra9+ 9 _!
 "w n o!rwise easily obta9$ outside ( a 

l>ge obs]vatory4 ,! lesson %\ld be      
taught t "t sp5t at a telescope is ne>ly
 wa/$1 unless results are secur$ wor?y (
 publication & hav+ a p]man5t value4 ,^?
 :o h once accompli%$ su* "w are likely 
9 ! future to appreciate its value1 & w 
(t5 cont9ue to d useful "w 9 "s o!r     
dep>tm5t ( practical a/ronomy1 if n 9 t 
( v>iable />s4 ,! education ( a class ( 
skill$ obs]v]s w\ld be a "w ( no less   
value ?an ! results anticipat$ f !      
obs]vation ( ! v>iable />s4  ,,edw>d ,c4
 ,,pick]+4  ,,h>v>d ,,college           
,,obs]vatory1 ,cambridge1 ,mass4